Invalid Sibling Link!!! What does it mean???


Invalid sibling link, it's all that Disk Utility, fsck (in apple-s mode) and DFA in OS 9.1 can say... they can't repair my disk. It's the 3rd time after i bought Mac OS X! The first was 5 days ago, and I've formatted my OS X partition, the second 3 days ago, and I've formatted, and the 3rd 10 minutes ago... WHY???
What is that "sibling link"???
And, with that error... I get the "unresolved kernel trap" on "" or something like that and another that I don't remember.
Please tell me if you know something about it, and above all, how to fix it up without formatting...

Bye and Thanks